Disc sanding apparatus



Dec. 17, 1968 M. MARTON DISC SANDING APPARATUS 2 Sheets-Sheet 1 Original Filed Feb. 24, 1967 R w N E u N I NlIfSH HRRTOIV ATTORNEyS Dec. 17, 1968 M. MARTON 3,416,265

DISC SANDING APPARATUS Original Filed Feb. 24, 1967 2 Sheets-Sheet 2 INVEIVTDR um; nnRT amen/5y:

United States Patent 3,416,265 DISC SANDING APPARATUS Miksa Marton, 27 Waverley Drive, Brockville, Ontario, Canada Application Feb. 24, 1967, Ser. No. 618,398, now Patent No. 3,378,961, dated Apr. 23, 1968, which is a continuation-in-part of application Ser. No. 467,275, June 28, 1965. Divided and this application Sept. 19, 1967, Ser. No. 668,850 Claims priority, application Canada, Oct. 21, 1966,

973,694, Patent 772,369

Claims. (Cl. 51381) ABSTRACT OF THE DISCLOSURE A disc-shaped mounting member for a rotary sander and a circular sheet of sand paper material adapted to be mounted thereon. The disc-shaped member is provided with a groove in its peripheral side wall to receive an elastic band and the circular sheet of sand paper has a non-abrasive peripheral portion adapted to be folded about the side wall of the mounting member so as to overlie the groove and be retained by the elastic band placed therearound. A central recess is provided in the mounting member and a central aperture is provided in the sheet so that the sheet can be centered with respect to the mounting member through the use of a removable guide rod extending through the aperture into the recess.

This is a division of application Ser. Nov 618,398, filed Feb. 24, 1967, now Patent No. 3,378,961 which is a continuation-in-part of application Ser. No. 467,275, filed June 28, 1965, entitled, Disc Sanding Apparatus (now abandoned).

This invention relates to mounting a sheet of material on a mounting member, and in particular to a sheet of sandpaper for use on a disc sander mounting member.

In the past, two methods have commonly been used for attaching sandpaper to a disc sander mounting member. In one method a sandpaper disc was bolted to the pressure face of a mounting member by means of a bolt and washer projecting from the mounting member at its centre. In the second method, a sandpaper disc was glued to the pressure face. Since the bolthead and washer projected past the surface of the sandpaper disc, it was impossible to use the centre of the sandpaper disc for sanding, and further, the projecting bolt rendered it diflicult in many circumstances to use even the edge of the disc with ease. In addition, when lighter grades of sandpaper were used, they tended to tear loose from the clamping bolt and washer. Recessing the bolthead and washer below the surface of the sandpaper disc normally required an expensive form of manufactured sandpaper, and the problem of tearing of the sandpaper still existed.

In the second commonly used method, a sandpaper disc was glued to the pressure face of a mounting member. This had the disadvantage that the sandpaper tended to tear and dust tended to get beneath its surface, thus weakening the glue so that the sandpaper came off the mounting member. If the sandpaper disc were glued sufliciently firmly to the mounting member to be able to restrict normal sanding stresses, then it became difficult to remove the sanding disc for replacement.

It has now been found that it is advantageous to attach the sandpaper to the mounting member by means of a flexible retaining member which cooperates with an annular groove in the mounting member. The flexible ring can be placed on the mounting member manually but this is somewhat tedious and time consuming.

The object of the present invention is to provide a ice mounting member, an apparatus for quick and easy mounting of a sanding disc on a mounting member, and a sanding disc particularly suitable for use with the mounting member.

Accordingly, the present invention relates to a sanding disc for use with a disc-shaped mounting member having a front pressure face having a diameter less than that of said sanding disc and a peripheral side wall ex tending rearwardly from said pressure face, the side wall having a groove extending therearound to receive an annular retaining member and the mounting member being provided with a centrally located cavity extending rearwardly from the pressure face; the sanding disc comprising a flexible web of non-abrasive material provided with circular abrasive surface on one face thereof whereby a peripheral portion of said disc is non-abrasive and adapted to be folded rearwardly about the circumference of the side wall of the mounting member to form a series of pleats around said side wall, the disc defining centering means in the form of a centrally located aperture of approximately the same diameter as the cavity in the mounting member so that the aperture and the cavity are aligned when a cylindrical guide member is inserted through the aperture into said cavity.

In the drawings:

FIGURE 1 is a partly sectional perspective view of one form of apparatus in accordance with the invention,

FIGURE 2 is a top plan view of the apparatus of FIGURE 1,

FIGURE 3 is a partly sectional perspective view of the disc sander with a sand paper disc mounted thereon, and

FIGURE 4 is a sectional perspective view of an alternate form of the apparatus of FIGURE 1.

Referring to FIGURE 1, there is shown a preferred form of a mounting member 1, a sheet of sandpaper 2 and a mounting apparatus generally indicated at 3.

The mounting member 1 is made of relatively resilient material, such as rubber, and includes a relatively thin disc 4 with a front pressure face 5 and a peripheral side wall 6 extending rearwardly from the pressure face 5. The side wall 6 is provided with a groove 7 extending therearound and spaced substantially uniformly from the pressure face 5. An outwardly extending spindle 8 is provided on a rear surface 9 of the member 1 for connecting the lattter to a motor driven chuck, or the like, for rotation of the member.

The pressure face 5 is preferably formed of a layer of sponge rubber 541 secured to the disc 4. The sandpaper sheet 2 is circular and preferably includes a pair of sandpaper discs 10, having a diameter slightly greater than the diameter of pressure face 5. One of the sandpaper discs 10 is mounted, such as by gluing, on each face of a flexible non-abrasive backing sheet 11 made of fabric or the like. The sheet 11 has a larger diameter than the discs and thus includes a peripheral free edge portion 12. It will be appreciated of course that abrasive may be secured directly to one or both faces of the backing sheet 11.

The mounting apparatus 3 includes upper and lower members 13 and 14, respectively, in the form of con centric cylinders, the upper 13 of which is telescopically mounted in the lower cylinder 14.

The uppper member 13 includes a base 15 and a peripheral side wall 16 extending upwardly from the base 15 for receiving a flexible retaining member 17. The outer end 18 of cylinder 13 is open defining a mouth for receiving the sandpaper sheet 2 and the mounting member 1. The height of side wall 16 is slightly less than, but approximately equal to the distance between the front pressure face and the groove 7 of the mounting mem- 3 her 1. The base 15 of the cylinder 13 is provided with an aperture 19 and an integral downwardly rojecting tube 20 coaxial with the aperture 19.

The lower cylinder 14 includes a side wall 21 and a base 22. The base 22 is provided with an aperture 23 axially aligned with aperture 19 in the base 15 of cylinder 13. A collar 24, co-axial with aperture 23, projects upwardly from base 22 for receiving tube 20. The free end 25 of tube 20 is provided with a cotter pin 26 passing through suitable aligned apertures therein which limits the movement of the upper cylinder 13 outwardly from the lower cylinder 14. A coil spring 27 surrounds tube 20 and bears against bases 15 and 22 to bias the upper cylinder 13 outwardly from the lower cylinder 14.

The apparatus of FIGURE 1 further includes a guide rod 28 spring mounted in the tube 20. The inner end of guide rod 28 is provided with a base 29 having a diameter slightly less than that of the internal diameter of the tube 20. The base 29 and guide rod 28 are biased outwardly of the tube 20 by a spring 30 disposed in the tube 20 between the base 29 and a disc 31 is held in the tube 20 adjacent the lower end thereof by the cotter pin 26.

With reference to FIGS. 1 and 2 it will be noted that a false bottom in the form of a circular plate 15a having a centrally located aperture 19a, is provided in the upper cylinder 13. The base 15 is provided with three or more adjustment screws 45 (two of which are shown) extending through suitable threaded apertures in bosses 46. The plate 15a rests on the heads of the screws 45.. Access to the heads of the screws is facilitated by the provision of holes 47 in the plate 15a.

The sandpaper sheet 2 is provided with a central aperture 32 through which the guide rod 28 can pass to properly align the sandpaper sheet and the upper cylinder 13.

The mounting member 1 includes a cavity 33 in the centre of the front pressure face for receiving the rod 28 to aligmthe mounting member with the apparatus and with the sandpaper sheet 2.

If a softer pressure face is desired, a further disc 40 of sponge rubber or the like having a centrally located aperture 41 may be provided. However the disc 40 is not permanently secured to the disc 4 as will be explaned below.

It will be particularly noted that in the apparatus of FIGURE 1 and FIGURE 2 the mating faces of the walls of cylinders 13 and 14 are each provided with alternate interfitting grooves 36 and splines 37. It will also be noted that the retaining member 17 is received on the splines 37 of the upper cylindrical member 13 for reasons to be discussed below.

The use of the apparatus 3 of FIGURE 1 is as follows. The retaining member 17 is stretched and placed around the outside circumference of the upper cylinder 13 adjacent the outer end 18 thereof. The sandpaper disc is placed on the mouth of cylinder 13 with the disc centered with respect to the interior of side wall 16 of the cylinderby the guide rod 28 which extends through the aperture 32. The sponge rubber disc 40 and the mounting member 1 are then placed in position over the sandpaper disc 10 so that the guide rod 28 extends into the cavity 33 and is then pushed quickly down into cylinder 13 thus pressing the disc 10 against the pressure face and folding the peripheral free edge 12 of the sandpaper sheet 2 over the side wall 6 of the mounting member 1. It will be noted that the spring 30 associated with guide rod 27 permits moving of the guide rod 28 simultaneously with the upper cylinder 13. Almost simultaneously, the pressure face bears against the base a of the cylinder 13 forcing the latter into cylinder 14 against the action of spring 27. As cylinder 13 enters cylinder 14 the retaining member 17 is forced along the wall 16 of cylinder 13 by the upper edge of side wall 21 of lower cylinder 14. When the upper edges of side walls 16 and 21 are approximately flush with each other the retaining member 17 is free to move into the groove 7 and in so doing urges the sandpaper sheet 2 against the mounting member 1.

When the mounting member 1, with the sandpaper sheet secured thereto, is removed from the cylinder 13, the latter is urged outwardly of the cylinder 14 by the coil spring 27. The outward movement of the cylinder 13 is limited by the pin 26 which permits the outer end 18 of the side wall 16 of cylinder 13 to extend beyond the cylinder 14 an amount sufficient to receive ring 17, but does not permit the cylinder 13 to escape outwardly from the cylinder 14.

It will be noted that when the sandpaper sheet 10 is so installed, the peripheral portion 12 has a number of pleats formed therein as it is urged against the side wall 6. These pleats assist the clamping action of the retaining member 17 in holding the sandpaper 2 to the mounting member 1, and since the pleats do not extend over the pressure face 5 to any appreciable extent, due to the inward taper of the side wall, they do not interfere with sanding close to surfaces perpendicular to the work surface. The sandpaper when held on in the fashion shown will sustain tearing in numerous locations before coming dislodged from its mounting.

If a harder pressure face is desired, the disc 40 is placed in the cylinder 13 under the sandpaper disc 10 so that the groove 7 will be aligned with the end 18 of the cylinder 13. However, the sponge rubber disc 40 will not be secured to the pad by the sandpaper disc 10 as illustrated in FIG. 3 but will remain in the cylinder 13.

Due to the fact that the retaining member 17 is preferably resilient material such as rubber the member 17 might tend to slip in between the upper cylinder 13 and the lower cylinder 14 as the cylinder 14 is forced into the cylinder 13 if the splines 37 were not provided. The splines 37 of the lower cylinder 14 extend radially inwardly of the retaining member 17 thus ensuring that the retaining member 17 is forced off the upper cylinder 13.

The apparatus of FIG.l provides for adjustment of the depth of the upper cylinder 13 in the event that a mounting member having a thickness greater or lesser than the mounting member 1 is used. As indicated above it is important that the effective depth of the cylinder 13 be substantially equal to the distance between the front pressure face and the groove 7 of the mounting member 1. Accordingly if adjustment is required, a screw driver is inserted through the holes 47, in the circular plate and the height of the srews 45 advanced or retracted so that when the plate again rests on the heads of the screws 45 the effective depth of the cylinder 13 will be compatible with the mounting member to be used.

It will be appreciated that the rubber retaining member 17 for use with an eight inch diameter mounting member may have a cross-sectional diameter of approximately one quarter of an inch. Since considerable force is required to stretch such a rubber member, a hook 49 is provided to retain the rubber member at one point on the circumference of the cylinder 13 as the member 17 is being stretched therearound.

The hook 49 is preferably fabricated of spring steel and is secured to the lower cylinder 14 as by machine screws. A terminal portion 48 of the hook 49 is disposed immediately adjacent to and parallel with the upper cylinder 13 to prevent escape of the rubber member 17 until the cylinder 13 is moved downwardly during the final step of mounting the sandpaper 2 on the member 1 described in detail above.

A simplified form of the apparatus of FIG. 1 is shown in FIG. 4 including a mounting member 51, a sheet of sand paper 52 and a mounting apparatus generally indicated at 53.

The mounting member 51 is similar to the mounting member 1 described with reference to FIG. 1 and includes a front pressure face 54, a peripheral side wall 56, a groove 58 extending therearound and a spindle 55. A resilient retaining element 64 in the form of a rubber ring in shown in place on the mounting apparatus 53.

The sheet of sandpaper 52 includes at least one central sanding disc 74 of ordinary sandpaper secured as by gluing to a flexible non-abrasive backing sheet 76 of fabric or tough plastic. The backing sheet 76 has a greater diameter than the sandpaper 74 and thus a peripheral portion 78 is provided.

It will be noted that the mounting member 51 and the sheet of sandpaper 52 are not provided with apertures such as the apertures 32 and 33 in the mounting member 1 and sandpaper 2 respectively of FIG. 1. This is due to the fact that the mounting apparatus 53 has no cen tral guide rod such as the guide rod 28 shown in FIG. 1. The apparatus 53 shown in FIGURE 4 includes a shallow cylinder or application member 80 of diameter just greater than the outer diameter of the mounting member 52. Cylinder 80 preferably includes a fiat bottom 82 and a generally upright rim or wall 84 joining the bottom 82 in a slightly curved area to conform to the curve that the sandpaper will make as it is folded around the peripheral edge of pressure face 54. The effective height of the rim 84 internally is approximately equal to the distance between the pressure face 54 and the peripheral groove 58 of the mounting member 51.

The use of the device shown in FIGURE 4 is as follows. The resilient ring 64 is stretched and placed in position around the outside circumference of the cylinder 80. A sandpaper disc 52 is then placed on and centered with respect to the upper surface of the rim 84. The mounting member 51 is then placed in position over the sandpaper disc 52 and pushed down into the cylinder 80 to a position adjacent the bottom thereof, thus forcing the peripheral portion 78 of the sandpaper disc 52 to fold upwardly over the side wall 56 of the mounting member 51. The ring 64 is then rolled upwardly over the upper edge of the cylinder 80 to fall into the curved groove 58 so that it clamps the sandpaper disc 52 to the mounting member 51.

It is possible to provide the cylinder 80 with a guide pin similar to the guide pin 28 shown in FIG. 1 thus facilitat ing its use in assembling a sanding disc 2 on a mounting member 1. Theguide pin would then be received in apertures 32 and 33 respectively of the disc 2 and member 1 to align the mounting member and disc. Aligning the mounting member and the sandpaper disc 2 is diflicult because the sandpaper sheets preferably extend beyond the periphery of the pressure face 5 of the mounting member 1 to prevent the fabric backing sheet 11 from contacting the work surface. Furthermore the inside diameter of the cylinder 80 is greater than the diameter of the mounting member 1 and the cylinder 80 is hidden by the peripheral portion 12 of the sandpaper sheet 2, thus a centrally located aligning means is extremely desirable.

I claim:

1. A sanding disc for use with a disc-shaped mounting member having a front pressure face having a diameter less than that of said sanding disc and a peripheral side wall extending rearwardly from said pressure face, said side wall having a groove extending therearound to receive an annular retaining member and said mounting member being provided with a centrally located cavity extending rearwardly from said pressure face; said sanding disc comprising a flexible web of non-abrasive material provided with a concentric circular abrasive surface on at least one face thereof whereby a peripheral portion of said disc is non-abrasive and adapted to be folded rearwardly about the circumference of said side Wall of said mounting member to form a series of pleats around said side wall, said disc defining centering means in the form of a centrally located aperture of approximately the same diameter as said cavity in said mounting member so that said aperture and said cavity are aligned when a cylindrical member is inserted through said aperture into said cavity.

2. A sanding disc as claimed in claim 1 for use with a mounting member wherein concentric circular abrasive surfaces are provided on both faces of said disc.

3. A sanding disc as claimed in claim 1 for use with a mounting member wherein said circular abrasive surface comprises a sandpaper disc adhesively secured to said flexible web and wherein said web is textile material.

4. In combination a sanding disc and a disc-shaped mounting member having a front pressure face having a diameter less than that of said sanding disc and a peripheral side wall extending rearwardly from said pressure face, said side wall having a groove extending therearound receiving an annular elastic retaining member and said mounting member being provided with a centrally located cavity extending rearwardly from said pressure face; said sanding disc comprising a flexible web of non abrasive material provided with a concentric circular abrasive surface on at least one face thereof having a diameter greater than the diameter of said pressure face, a peripheral portion of said disc being non-abrasive and folded rearwardly about the circumference of said side wall of said mounting member to form a series of pleats around said side wall, said disc defining centering means in the form of a centrally located aperture of approximately the same diameter as said cavity in said mounting member so that said aperture and said cavity are aligned when a cylindrical member is inserted through said aperture into said cavity.

5. The combination claimed in claim 4 wherein concentric circular abrasive surfaces are provided on both faces of said disc.

6. The combination claimed in claim 4 wherein said circular abrasive surface comprises a sandpaper disc adhesively secured to said flexible web and wherein said web is textile material.

7. The combination as claimed in claim 4 wherein a sponge rubber disc of the same diameter as said pressure face and having a centrally disposed aperture therethrough is provided between said pressure face and said sanding disc, said sponge rubber disc being held in place by said sanding disc and said annular retaining member.

8. In an assembly for detachably securing a sanding disc to a mounting member wherein the assembly includes apparatus having a central aligning guide for the application of the disc to the member, an improved mounting member comprising:

(a) a circular front pressure face adapted to have a circular sheet of abrasive material secured thereto;

(b) a peripheral side wall extending rearwardly and tapering inwardly from the pressure face;

(c) a circumferential groove in the tapered side Wall adapted to accommodate a peripheral portion of the disc and a resilient disc retaining member therein;

(d) a centrally located cavity in the pressure face adapted to receive the assembly guide for accurately centering and aligning the disc on the mounting member; and

(e) the diameter of the pressure face of the mounting member being less than that of the abrasive material secured thereto.

9. A mounting member as claimed in claim 8 where in said portion of said mounting member defining said pressure face comprises flexible resilient rubber like material.

10. A mounting member for use with a substantially circular sanding disc having an abrasive centre section and a non-abrasive flexible peripheral portion therearound; said mounting member comprising:

(a) a front pressure face;

(b) a peripheral side wall extending rearwardly and tapering inwardly from the pressure face; and

(c) a peripheral circumferential groove in the rearwardly and inwardly tapering side wall;

(d) said front pressure face and the peripheral side wall, at least, of the mounting member being formed of a resilient flexible material; and

(e) a centrally located cavity in the mounting member References Cited extending normal to and inwardly from the front UNITED STATES PATENTS pressure face thereof;

the pressure face having (i) a diameter no greater than kjg gg that of the abrasive centre section of the disc and 5 505644 9/1893 Webster 51 381 (ii) being adapted to receive the abrasive section of 2,127:703 8/1938 Schwenke 51 381 the disc in an overlying relationship; the tapered pe- 2,225,053 12/1940 Hope ripheral side wall of the mounting member being 3 1 5 6/1965 Ball X adapted to receive the flexible peripheral portion of the disc in an overlying pleated arrangement; and 10 ROBERT C. RIORDON, Primary Examiner. the peripheral circumferential groove being adapted KELLY, Assistant Examiner to accommodate the flexible peripheral portion of the disc together with an-elastic annular member for US. Cl. X.R. retaining that portion therein. 15 

